atomic weight

noun

: the mass of one atom of an element

specifically : the average mass of an atom of an element as it occurs in nature that is expressed in atomic mass units see Chemical Elements Table

Example Sentences

Recent Examples on the Web Many periodic tables include the atomic number (number of protons) and atomic weight (which depends on protons and neutrons). —

Bill Andrews, Discover Magazine, 26 June 2019 Specific trends, such as melting point and atomic radius, recur periodically among the elements when they’re listed in order of increasing atomic weight. —

Bill Andrews, Discover Magazine, 26 June 2019 Lead, with its heavy atomic weight, interferes with all of this as it gets swapped in for blood cells, neurons, and other crucial bits of biology. —

Michael J. Coren, Quartz, 16 June 2022 Plain ol’ carbon — carbon that has 6 protons and 6 neutrons for an atomic weight of 12 — is far more stable than radiocarbon, and therefore vastly more plentiful in Earth’s atmosphere. —

Rebecca Coffey, Forbes, 3 Mar. 2021 Kaiser and his colleagues chose rhenium because each atom is relatively large, compared more familiar atoms like carbon and oxygen that are less than one tenth of its atomic weight. —

Theresa Machemer, Smithsonian Magazine, 22 Jan. 2020 This approach succeeds most of the time, when the issue is, say, the atomic weight of hydrogen. —

Adrian Bardon, Scientific American, 26 June 2020 The atomic weight of the sun is composed of 92.1 percent hydrogen and 7.8 percent helium, with traces of carbon and nitrogen. —

Jennifer Leman, Popular Mechanics, 3 Nov. 2019 How to Read the Table Many periodic tables include the atomic number (number of protons) and atomic weight (which depends on protons and neutrons). —

Bill Andrews, Discover Magazine, 26 June 2019 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'atomic weight.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

First Known Use

1819, in the meaning defined above

Time Traveler

The first known use of atomic weight was in 1819

See more words from the same year

Cite this Entry

Style

“Atomic weight.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/atomic%20weight. Accessed 23 Mar. 2023.

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